Marsha has two numbers, $a$ and $b$.  When she divides $a$ by 70 she gets a remainder of 64.  When she divides $b$ by 105 she gets a remainder of 99.  What remainder does she get when she divides $a+b$ by 35?
Explanation: Marsha has two equations: \[a=70n+64\]and \[b=105m+99.\]When she adds these she gets \begin{align*}
a+b&=70n+105m+64+99 \\
&=35(2n+3m)+163=35(2n+3m+4)+23.
\end{align*}The remainder when $a+b$ is divided by 35 is $\boxed{23}$.